What batteries are folks using for smoke alarms?

I have been using the Lithium 10 year batteries and I only get 2 to 3 years before the low battery alert goes off. The alarms had Duracell Ultra batteries from new, but those are no longer available. The lithium batteries are over $6 each and I don't think they last three times longer than alkalines. I have had to replace three batteries in the past 60 days.

The interesting thing is that my smoke alarms are all AC powered with battery backup. I don't understand how I am burning through batteries since I am not losing power. These are smoke/CO detectors with voice alerts.

The low battery alert is very annoying as they beep and then a voice says "Low Battery".